Biomass and nutrient removal by willow clones in experimental bioenergy plantations in New York State

The development of short-rotation intensive cultural (SRIC) willow systems as a source of bioenergy and bioproducts is growing in the northeastern and midwestern United States. Important data for sustainable management such as nutrient removal and nutrient use efficiency in willow bioenergy plantations is lacking. This study reports wood biomass production, annual removal of nutrients, and nutrient use efficiency in experimental plantings of SRIC willow and poplar at Tully, New York. Effects of clone, fertilization, irrigation, planting density, and harvest cycle were analyzed.

Annual biomass production of 15–22 dryMg/ha removed 75–86, 10–11, 27–32, 52–79 and 4–5 kg/ha/year of N, P, K, Ca and Mg, respectively. For all the variables studied, the responses depended on clone. Fertilization and irrigation increased rates of nutrient removal by means of increased biomass production. Unlike planting density, harvest cycle significantly affected rates of nutrient removal and nutrient use efficiency. For clone SV1 (Salix dasyclados), an irrigated and fertilized planting with a density of 36,960 trees/ha harvested on a 3-year rotation had the highest biomass production and nutrient use efficiency, and the lowest rates of nutrient removal. The annual harvest cycle had the lowest nutrient use efficiency and the highest annual removal of nutrients suggesting that this choice would be most appropriate for biomass crops that are to be used as buffer strips to manage nutrient runoff from agricultural fields. An appropriate choice of clone, planting density, and harvest cycle could tailor the rates of nutrient removal and nutrient use efficiency to match the objective of the planting.